Papers by Keyword: Surface Morphology

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Authors: Yong Qiang Sun, Gan Feng, Li Ping Lv, Wei Ning Qian, Yi Yang Li, Jin Yun Luo, Jian Hui Zhang
Abstract: Homo-epitaxial growth of 4H-SiC on 4o off-axis 150 mm diameter substrates has been performed in a commercial warm-wall multi-wafer planetary reactor. Based on our well developed 100 mm 4H-SiC epitaxial growth process, which can achieve excellent thickness and doping uniformities (δ/mean) of <1% and <5%, respectively, the growth process and hardware were further fine-tuned and improved for 150 mm 4H-SiC homoepitaxy. After the improvement, the 6 to7 μm thick epilayer uniformity has reached 1.1% with a 5mm edge exclusion while the doping uniformity has improved to 16.5% (<10%) with an edge exclusion of 5 mm (10mm), respectively. Surface roughness of the as-grown 150 mm 4H-SiC epitaxial layer has an RMS value of 0.12 nm scanned by AFM on 20×20 μm2 areas. Homo-epitaxial growth on C-face 150 mm 4H-SiC substrates has also been carried out. Other than the doping concentration and uniformity, the other results are very close to the epi-growth on Si-face.
Authors: Byeung C. Kim, Michael A. Capano
Abstract: Cubic silicon carbide (3C-SiC) growth using Pendeo-epitaxy technique was successfully achieved on Si(001) substrates. 3C-SiC was grown by chemical vapor deposition (CVD) with silane and propane as precursors. Effects of underlying stripes and seed 3C-SiC layers thickness on PE 3C-SiC films were investigated. Root mean square (RMS) measurements using atomic force microscope (AFM) showed that surface morphology of PE 3C-SiC films remarkably improves with an increase of the seed 3C-SiC layer thickness, and the values were from 9.8 nm for 3 µm thick seed layer to 0.5 nm for 10 µm thick seed layer thickness. Additionally, domain boundary densities were counted, and the values also strongly depend on the seed layer thickness: from >1500/mm2 for 3 µm seed layer thickness to <100/mm2 for 10 µm seed layer thickness. Pendeo-epiaxial growth profiles with various width/separation dimensions of stripes were also investigated, and stripes with width of 10 µm and separation of 5 µm provide the best profile and process viability.
Authors: Hitoshi Habuka, Yusuke Katsumi, Yutaka Miura, Keiko Tanaka, Yasushi Fukai, Takaya Fukae, Yuan Gao, Tomohisa Kato, Hajime Okumura, Kazuo Arai
Abstract: The etching technology for 4H-silicon carbide (SiC) was studied using ClF3 gas at 673-973K, 100 % and atmospheric pressure in a horizontal reactor. The etch rate, greater than 10 um/min, can be obtained for both the C-face and Si-face at substrate temperatures higher than 723 K. The etch rate increases with the increasing ClF3 gas flow rate. The etch rate of the Si-face is smaller than that of the C-face. The etched surface of the Si-face shows many hexagonal-shaped etch pits. The C-face after the etching is very smooth with a very small number of round shaped shallow pits. The average roughness of the etched surface tends to be small at the higher temperatures.
Authors: Akira Miyasaka, Jun Norimatsu, Keisuke Fukada, Yutaka Tajima, Yoshiaki Kageshima, Daisuke Muto, Michiya Odawara, Taichi Okano, Kenji Momose, Yuji Osawa, Hiroshi Osawa, Takayuki Sato
Abstract: The production of 150 mm-diameter SiC epitaxial wafers is the key to the spread of SiC power devices. We have developed production technology of the epitaxial growth for 4° off Carbon face (C-face) 4H-SiC epitaxial layers on 150 mm diameter substrates. Several growth parameters and hardware were optimized to obtain high uniformity wafers. We have succeeded in fabricating high quality C-face wafers with smooth surface and high uniformity.
Authors: Takeshi Mitani, Naoyoshi Komatsu, Tetsuo Takahashi, Tomohisa Kato, Toru Ujihara, Yuji Matsumoto, Kazuhisa Kurashige, Hajime Okumura
Abstract: We have investigated the solution growth under various Al-N co-doping conditions. Both p-type and n-type 4H-SiC were successfully grown under Al-N co-doping conditions, while using the effect of Al-addition to stabilize both growth surface and polytype. The doping and electrical properties were investigated systematically. Interaction between Al and N in the incorporation process and electrical property under heavily co-doped conditions were discussed.
Authors: Yong Qiang Sun, Gan Feng, Zhe Yang Li, Li Ping Lv, Jin Yun Luo, Jin Bo Wu, Yi Yang Li, Jian Hui Zhang
Abstract: Homo-epitaxial growth of 50 μm-thick 4H-SiC on 4° off-axis 100 mm substrates have been demostrated by using a commercial warm-wall multi-wafer planetary reactor (Aixtron 2800 G4). With optimized process, epitaxial layer with an average thickness of 48.146 μm and doping level of 8.39×1014/cm3 are obtained. The thickness uniformity with an edge exclusion of 5 mm are 1.30% (σ/mean) and 2.17% (max-min/max+min), and the doping level uniformity are 4.66% (σ/mean) and 6.95% (max-min/max+min), respectively. Surface roughness of the as-grown 50 μm-thick epitaxial layer has an RMS value of 0.606 nm with one step bunching on the 20×20 μm2 areas. This initial effort on thick 4H-SiC homoepitaxial growth indicates that this comercial multi-wafer planetary reactor has the potential for mass production of SiC epiwafers for 5000 V and above power devices.
Authors: Sung Jin Cho, Cong Wang, Nam Young Kim
Abstract: In the process of characterizing AlGaN/GaN HEMTs on Si (111), Sapphire, 4H-SiC substrates, various Rapid Thermal Annealing (RTA) conditions for the Ti/Al/Ta/Au ohmic contact process and the resulting surface analysis have been investigated. In order to achieve a low ohmic contact resistance (RC) and a high quality surface morphology, we tested seven steps (800 °C to 920 °C) annealing temperatures and two steps (15, 30 sec) annealing times. According to these annealing temperatures and times, the optimal ohmic resistance of 3.62 × 10-6 Ohm • cm2 on Si(111) substrate, 9.44 × 10-6 Ohm • cm2 on Sapphire substrate and 1.24 × 10-6 Ohm • cm2 on 4H-SiC substrate are obtained at an annealing temperature of 850 °C and an annealing time of 30 sec, 800 °C and an annealing time of 30 sec and 900 °C and an annealing time of 30 sec, respectively. The surface morphologies of the ohmic contact metallization at different annealing temperatures are measured using an Atomic Force Microscope (AFM). AFM morphology Root Mean Square (RMS) level determines the relationship of the annealing temperature and the annealing time for all of the samples. According to these annealing temperatures and times, the optimal ohmic surface RMS roughness of 13.4 nm on Si(111) substrate, 3.8 nm on Sapphire substrate and 2.9 nm on 4H-SiC substrate are obtained at an annealing temperature of 850 °C and an annealing time of 30 sec, 800 °C and an annealing time of 30 sec and 900 °C and an annealing time of 30 sec, respectively.
Authors: Giovanni Attolini, Bernard Enrico Watts, Matteo Bosi, Francesca Rossi, Ferenc Riesz
Abstract: A comparative study of the morphology of 3C-SiC films prepared with different C:Si ratios is presented. The silane precursor controls the growth rate at all values of C:Si ratio but combined of observations using Atomic Force Microscopy (AFM) and Scanning Electron Microscopy (SEM) indicates that the C:Si ratio is critical in determining the grain size and at values of C:Si close to 1 texturing and faceting become evident. Makyoh Topography reveals various surface defects, a slight mesoscale roughness and bending of the epiwafers.
Authors: Viboon Tangwarodomnukun, Jun Wang, Philip Mathew
Abstract: Laser micromachining has been widely used for decades to fabricate the micro- and submicro-component structures. However, thermal and physical damages are crucial issues associated with the process. Underwater laser ablation has been developed as a damage-free micro-ablation technique. In this paper, a comparison of the conventional dry and underwater laser micromachining of silicon is presented. It shows that the heat affected zone (HAZ) can be reduced significantly in the underwater laser process, though the material removal rate is reduced due to the energy loss by the water layer. The effects of pulse frequency, traverse speed and laser energy on the obtained kerf width, HAZ and cut surface quality are also analyzed and discussed.
Authors: Christopher L. Frewin, Camilla Coletti, Christian Riedl, Ulrich Starke, Stephen E. Saddow
Abstract: A comprehensive study on the hydrogen etching of numerous SiC polytype surfaces and orientations has been performed in a hot wall CVD reactor under both atmospheric and low pressure conditions. The polytypes studied were 4H and 6H-SiC as well as 3C-SiC grown on Si substrates. For the hexagonal polytypes the wafer surface orientation was both on- and off-axis, i.e. C and Si face. The investigation includes the influence of the prior surface polishing method on the required etching process parameters. 3C-SiC was also studied grown in both the (100) and (111) orientations. After etching, the samples were analyzed via atomic force microscopy (AFM) to determine the surface morphology and the height of the steps formed. For all cases the process conditions necessary to realize a well-ordered surface consisting of unit cell and sub-unit cell height steps were determined. The results of these experiments are summarized and samples of the corresponding AFM analysis presented.
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